If the cap fits…

Musicians love to talk about their gear the same way (some) women like to talk about kittens and knitting.
In the old days, this was fairly manageable. The discussion usually comprised two old musos in the pub…

"Valve amps are better than transistor amps."
"No they're not."
"OK. Fancy another pint?"

Now, with the Internet, the debate has got out of hand. It's like a global crusade combined with the Spanish Inquisition. Everyone's got a view, but rarely agrees with anyone else, except to gang up and flame some poor 16 year-old for having the 'wrong' opinion.

Capacitors cause a worrying amount of debate in this area, perhaps because the signal appears to 'pass through' them on its journey through the amp. It doesn't really, but caps can affect tone because they charge at different rates, etc.

Actually decent audio caps at the kind of voltage ratings you need in a valve amp are not that widely available. I like to use Sprague Orange Drops, which I import wholesale from the USA... better than the usual little poly caps, and yes I can hear the difference and so will you, especially in high gain amps with plenty of stages for the signal to pass through.

I do think there is a slight sound difference with carbon composition resistors too (though admittedly I do feel a bit of a tosser saying this), and if I'm building an amp I use them wherever they're near the signal path and carry significant voltage (they can't make a difference if they don't, as far as I can see).

But they are hard to get and cost up to 100 times more than the quieter, utterly reliable little film types that every commercial amp uses, so I don't sweat it. Anyhow I'm probably imagining the sound difference; we're all a bit susceptible to vintage amp voodoo and I'm no different. As yet I've remained immune to paper-in-oil caps, but that's no doubt because I've managed to avoid finding out where to get them.